Chronic wounds, such as pressure ulcers, venous ulcers and diabetic ulcers, are significant public health concerns. Within the United States, the annual incidence of such chronic wounds is greater than 7 million. Further, the incidence of these chronic wounds increases as much as 14% per year. This is particularly true for diabetic ulcers, which afflict about 15% of the 16 million diabetics in the United States. Each year, approximately 85,000 lower-extremity amputations are performed as a result of treatment failure of diabetic ulcers. Such chronic wounds occur in approximately 31% of diabetic patients and take up to 20 weeks to heal. The incidences of venous and pressure ulcers within the United States are estimated to be 1.3 million and 3 million, respectively, with an annual growth rate of about 6%.
Wound healing involves a series of interrelated events including coagulation, inflammation, deposition and differentiation of extracellular matrix, fibroplasia, epithelialization, contraction and remodeling. There are slight differences in the healing process depending on the type of wound. For example, the healing of a chronic pressure ulcer mainly involves deposition of extracellular matrix and contraction. However, a partial-thickness burn wound primarily heals through epithelialization. On the other hand, the healing of diabetic ulcers can be further complicated by other diabetic issues such as neuropathy, poor circulation and decreased response to infection.
Presently, chronic wound patients are faced with a lack of effective treatment options and a high cost of care. Currently available treatment methods for the type of wounds described above include various types of dressings, debridement/irrigation, pressure relieving devices, ultrasound, whirlpool/pulsed lavage, ultraviolet, pulsed frequency radiation, low-energy laser, hyperbaric or topically applied oxygen, cytokine growth factors, antibiotics and topical and systemic drugs. Research has also been centered on developing surgical glues, sealants and dressing, artificial skin and growth factors such as transforming growth factors (TGF-β), fibroblast growth factor (aFGF and bFGF), platelet-derived growth factor (PDGF), epidermal growth factor (EGF), insulin-like growth factors (IGF-I and IGF-II) and interleukins (IL-1 and IL-2). Other research has focused on reducing the pressure on the soft tissue by designing a variety of wheelchair cushions, pads, shoes, mattresses and beds to distribute the pressure more evenly over the body. Unfortunately, even with the best available wound care procedures, chronic wounds tend to heal very slowly, not heal at all, or even worsen.
An alternative approach to wound healing is the implementation of electrical stimulation. The rationale for using electrical stimulation is based on the fact that the human body has endogenous bioelectric systems that promote wound healing. However, when the body's endogenous bioelectric system is inadequate, external electrical stimulation can be used to supplement the natural bioelectric currents or electric fields for enabling or enhancing wound healing.
The exact mechanism by which capacitively coupled electrical stimulation enhances wound healing is not completely understood. However, it has been found that the biochemical pathway mediating cell response to capacitively coupled electrical stimulation involves the opening of voltage-gated calcium channels that allow a flow of calcium ions into the cell. The subsequent increase in intracellular calcium levels triggers the activation of a host of signal tranduction pathways. These processes include activation of calmodulin and release of several second messenger molecules, such as cyclic adenosine monophosphate (c-AMP) and prostaglandin E2. These molecules activate specific protein kinases including c-AMP-dependent protein kinase, calcium-calmodulin dependent protein kinase and protein kinase-C, which results in increased cell proliferation. Further, capacitively coupled electrical stimulation also promotes local growth factor synthesis, such as transforming growth factor-beta 1 (TGF-β1) by the calcium-calmodulin pathway, and can affect different types of growth factor receptors. The growth factor receptors have integrated tyrosine kinase activities, which can activate several intracellular proteins involved in cell proliferation.
There are several disadvantages associated with prior art methods of electrical stimulation for wound healing. One disadvantage is that many prior art methods require placement of one or perhaps two electrodes directly on the soft tissue wound. Such placement increases the probability of bacterial contamination, thereby complicating wound healing and further, acid or base build-up on the electrodes can adversely effect healing in the wound area. Other prior art devices and methods are inconvenient or difficult to employ as a result of their bulk or complexity. For example, several prior art devices require the implementation of several electrodes, whereby one electrode is applied directly over the wound area or immersed in a saline solution containing the body part with the wound and at least one other electrode is positioned on the patient as far away from the wound as possible. This makes extended treatment periods uncomfortable for the patient, as well as, prohibiting free travel of the patient.
Thus, it is desirable to provide an improved electrical stimulation method for promoting wound healing of soft tissue wounds, such as venous, diabetic and pressure ulcers. The method should treat the wound area without actual contact with the wound to reduce the probability of bacterial infection. Further, the method should be simple and inexpensive while effectively treating soft tissue wounds.